Coated foamable styrene polymer particles

ABSTRACT

FOAMABLE PARTICLES OF THE STYRENE POLYMERS AND A VOLATILE BLOWING AGENT AND A LIPOPHILIC SURFACE-ACTIVE COATING AGENT, WHEREIN THESE PARTICLES CONTAIN, AS A COATING AGENT, FROM 0.05 TO 0.5% BY WEIGHT, CACULATED ON THE BLOWING AGENT CONTAINING STYRENE POLYMER, OF MIXTURES OF MONO-, DI- AND TRI-ESTERS OF GLYCEROL WITH SATURATED FATTY ACIDS HAVING FROM 12 TO 22 CARBON ATOMS, OR MIXTURES THEREOF. THESE FOAMABLE PARTICLES OFFER AN ESSENTIAL   SHORTENING OF THE COOLING TIME DURING FOAMING, A BETTER BOND OF THE FOAMED PARTICLES AND A SUBSTANTIALLY UNIFORM DISTRIBUTION OF THE GROSS UNIT WEIGHT IN THE FOAM BLOCK.

Jan. 29, 1974 a. HElsKEL ETAL 3,789,028

COATED FOAMABLE STYRENE POLYMER PARTICLES Filed July 5. 1972 FIG. 1

- block width 50cm--- block width 50 cm United States Patent U.S. c1. zen-2.5 3 Claims ABSTRACT OF THE DISCLOSURE Foamable particles of the. styrene polymers and a volatile blowing agent and a lipophilic surface-active coating agent, wherein these particles contain, as a coating agent, from 0.05 to 0.5% by weight, calculated on the blowing agent containing styrene polymer, of mixtures of mono-, diand tri-esters of glycerol with saturated fatty acids having from 12 to.22 carbon atoms, or mixtures thereof. ,These foamable particles offer an essential shortening of the cooling time during foaming, a better bond of the foamed particles and a substantially uniform distribution of the gross unit weight in the finished foam block.

This present invention relates to foamable styrene polymer particles.

Before being processed, generally by pre-foaming, intermediate storage and foaming (final foaming) in molding tools, polystyrene particles containing blowing agents have to be treated with processing auxiliary agents in order to prevent clogging and the build-up of electrostatic charge during pre-foaming and to ensure suflicient flow capacity. It is customary to treat the pre-foamed particles with other additives, e.g., paraffin oils or waxes so as to shorten the cooling time in the molds and to render uniform the gross unit weight in the cellular plastics.

.G.B. Pat. No. 1,093,899 describes that by the blending of blow-agent-containing polystyrene particles with small amounts of a lipophilic surface-agent there is obtained a material which does not clog during pre-foaming and the cooling time of which during final foaming inmolds is reduced to about 50 to 80% of its original value. According to this patent, sorbit esters are preferably used, espe-' cially sorbit monoester of lauric acid, stearic acid, p-almitic acid or oleic acid. a

Now, there have been found foamable particles made from styrene polymers and a volatile blowing agent and a lipophilic surface-active coating agent, wherein the coating agents are mixtures of from 0.05 to 0.5% by weight, calculated on the blowing-agent containing styrene polymer, of -mono-, diand triesters of glycerol with saturated fatty acids having from 12 to 22 carbon atoms, or the mixtures thereof.

The ester mixtures which, according to the invention, are to be used as coating agent are the so-called glycerol fatty acid partial ester mixtures. The ester mixtures preferably contain from 30 to 60% by weight of monoester, from 30 to 60% by weight of diester and from 5 to 20% by weight of triester. There are especially employed glycerol ester mixtures of fatty acid mixtures such as obtained by hydrogenation and saponification of natural fats; these fatty acid mixtures consist mainly of stearic and palmitic acids. The glycerol-fatty-acid partial ester mixtures employed are prepared preferably by means of glycerinolysis of hydrogenated natural fats. Very good results are obtained also with mixtures of mono-, diand triesters of the glycerol with pure acids, for example, stearic or palmitic acid.

Patented Jan. 29, 1974 p ce The fo'amable styrene polymer particles of the invention contain the above-mentioned ester mixtures in an amount of from 0.05 to 0.5% by weight, preferably of from 0.1 to 0.3% by Weight, calculated on the blowingagent-containing styrene polymer.

As styrene polymers for the foamable particles of the invention there are particularly suitable polystyrene and copolymers of the styrene, having up to 30% by weight, preferably up to 20% by weight, preferably up to 20% by weight, of comonomers, for example methylstyrene and/ or acrylonitrile. 3 The foa mable particles contain generally of from 5 to 12% by weight of volatile blowing agents. Blowing agents are, for example, lowboiling hydrocarbons, such as npentane, i-pentane, or butane, or chlorohydrocarbons, such as dichloromethane and fiuorinated chlorohydrocarbons, such as difluoro-dichloromethane. There may be used as Well mixtures of these blowing agents. The hydrocarbons are preferably added in an amount of from 5 to 8% by weight and the halogenated hydrocarbons are added preferably in an amount of from 6 to 12% by weight.

The coating agents of the invention are applied, for example, by treating the blowing-agent-containing styrene polymer particles with solutions of the coating agent in a solvent or by applying the powdery coating agent onto the blowing-agent-containing styrene polymer particles, by means of rotating drums.

The foamable particles from styrene polymers of the invention offer an essential shortening of the cooling time during foaming compared to the state of the art, a better bond of the foamed particles and a subtsantially uniform distribution of the gross unit weight in the finished foam block.

I The following examples illustrate the present invention.

EXAMPLE 1 30 kg. of polystyrene beads (bead size from 0.4 to 2.5 mm., 85% thereof from 0.8 to 2 mm.; reduced specific viscosity (RSV value) determined at 25 C. by means of an Ubbelohde viscometer with a 1.25% solution in blender (Roland-kneader) with 60 g. (0.2% of a pow dery glycerol-fatty acid partial ester mixture, prepared by glycerinolysis of hydrogenated beef tallow, consisting of 45% by weight of monoester, 45% by weight of diester and 10% by weight of triester. This mixture was prefoamed in a pressure pre-foamer under a vapor pressure of 0.05 atmosphere gauge to yield a bulk density of from 13 to 14 g./l. No clogging was noticed. The prefoamed material which had very good properties, was pneumatically conveyed to a silo and after an intermediate storage time of 24 hours it was filled in a block mold having the following inside dimensions: 2.50 m. x 1.25 m. x 0.50 on.

After a thorough vapor deposition on the mold up to a stream pressure in the interior of the mold of 0.5 atmosphere gauge, there resulted a foam block having a. good bond, which, after a cooling time of 11 minutes, could be removed from the mold without subsequent deformation. The cooling time was determined by measuring the deformation of the mold sides. As soon as the deformation of the mold sides was zero, it was possible to remove the block from the mold without further deformation.

A piece of 20 cm. in thickness (dimensions 1.25 x 0.50 m. x 0.20 m.) was cut from the block center and the gross unit weight distribution was determined from the block width in the following way:

The removed piece was cut into stripes having each 5 cm. in thickness, vertically to the edge having a width of 50 cm.; the gross unit weight of the stripes was then determined (weight/volume). The gros unit weight distribution thus determined is represented in FIG. 1 (dia- TABLE 2 gram). With a minimum of 12.8 g./l. and'a maximum value of 14.5 g./l., the variation margin was only 1.7 g./l. Fatty acid fi l fi glycerol 'tlenldency C u M i tlillstl'ibfi- Variaes er c ogging 00 ng n mum on, tion Comparative Example for Example 1 5 mixture dun-mg pm time" value, (maxinflm margin, A 1 t d b1 t t 1 percent ,foamlng, 7 mm. g./1. value) commercra coa e owmg agen con ammg p0 ystyrene in the form of beads, containing 6.9% by weight gg if i fljj igg f ijjjjj 2i {S i 2:3 of pentane was prefoamed, stored for 24 hours and g g g 3-8 i? foamed into a blockof the same bulk as described in 10 jj ifij 3 3; 3 Example 1. A cooling time of 30 minutes was necessary x Com arison concentration mum ism to remove the block from the mold without further bulgp c ing. The variation margin of the gross unit weight dis- What 15 clalmed I tribution determined as in Example 1, was 3.9 g./l. with Foamable Partlclfis of styrene P a volatlle a minimum 'value of 412.1 g./l. and a maximum value of blowing agent a lipophilic surface'active coating 1 1 The graph f FIG 2 shows the gross unit 15 agent,,wherein the particles contain, ascoatifng agent, weight distribution from 0.05 to 0.5% by weight, calculated on the blowing- EXAMPLE 2 agent-containing styrene polymer, of a mixture of from 30 to 60% by weight of a monoester, 30 to 60% by In order to prove that the glycerol fatty acid partial W ght of a diestel and 5 t0 y Weight of iitfiestel' ester mixtures are superior to the sorbit esters used 20 of g y w a saturated fatty acid r a mixture f according to 0.13. Pat. No. 1,093,899, the substances saturated fatty acids having from 12 to 22 carbon-atomsused in this patent in Example 1 were tested in compari- 2- F b p ticles of styrene polymer according to son with a glycerol ester mixture. For this purpose, the claim 1, wherein the particles contain a coating agent in polystyrene of Example 1 was mixed with 0.15% of the an amount of from 0.1 to 0.3% by Weight, calculated different esters and pre-foamed, stored and finally foamed 25 n the l wi g styrene p ymer.

into blocks as described in Example 1. The resultsare 3. Foamable particles of styrene polymers as claimed shown in Table 1: in claim 1 wherein the particles contain as coating agent,

TABLE 1 Block properties Pro-foaming DIN 53 423 Gross Bulk Cooling unit Variation Flexural Deflection densitlgi, time, weigh}, margilrll, strength, at break,

Coating agent (0.15%) Properties mm. g./ kp,/em.' mm.

Glycerol-fatty-acid-partiel-ester mixture 1 Good 13.2 16 13.3 1.2 1.61 8.3 Borbit-monolaurate do 12.5 45 13.6 0.9 1 49 3. 3 Sorbit monopahnitate -do 13. 2 38 13. 8 1. 8 1. 51 6. 9 Sorbit-monostearate ..d0 13. 0 13. 2 1. 1 1. 49 6. 7

1 Prepared by glycerinolysis of hydrogenated coconut 011, 39% mono, 41% diand 20% of triester. 1 The sorbit-mono-laurate was mixed with the same amount 01 n-pentane and added to the polystyrene beads as described in Example 1 of British Patent No. 1,093,899.

* Slight difliculties with dosage.

There can be seen from the table that when utilizing 45 glycerol-fatty acid ester mixturesobtained by glycerinolyglycerol-fatty acid partial ester mixtures, the results will sis of hydrogenated natural fats. I

not only be a shorter cooling time but also better me-. R f Cit d properties of the finished block. P

EXAMPLE 3 2,989,782 6/ 19611 Barkutf, Jr., et al. 260-25 The same polyestyrene as in Example 1, containing, UL U BBRMAN, Primary Examiner however, only 6.9% by weight of petane, was mixed FOELAK, Assistant Examiner with dlfierent amounts of the same glycerol-fatty acid partial ester mixture of Example 1 and, as was described 5 CL there pre-foamed, stored and foamed to yield a block. The iesult is shown in Table 2. 117 100 C, 260-235 

